This clinical trial focuses on the use of phenylbutyrate, to treat patients with chronic liver disease and hyperammonemia. This drug removes ammonia via utilization of the amino acid acylation pathway. The availability of therapy aimed exclusively at ammonia removal is important for two reasons 1) a decrease in potential side effects as well as easier dosing would improve compliance and outcome in these patients, and 2) it could better define ammonia's role in encephalopathy.